India's HIV epidemic is not yet contained and prevention in populations most at risk (high-risk groups) needs to be enhanced and expanded. HIV prevalence as measured through surveillance of antenatal and sexually transmitted disease clinics is the chief source of information on HIV in India, but these data cannot provide real insight into where transmission is occurring or guide programme strategy. The factors that influence the Indian epidemic are the size, behaviours, and disease burdens of high-risk groups, their interaction with bridge populations and general population sexual networks, and migration and mobility of both bridge populations and high-risk groups. The interplay of these forces has resulted in substantial epidemics in several pockets of many Indian states that could potentially ignite subepidemics in other, currently low prevalence, parts of the country. The growth of HIV, unless contained, could have serious consequences for India's development. India's national response to HIV began in 1992 and has shown early success in some states. The priority is to build on those successes by increasing prevention coverage of high-risk groups to saturation level, enhancing access and uptake of care and treatment services, ensuring systems and capacity for evidence-based programming, and building in-country technical and managerial capacity.